Alcoutim's flower-ringed, 13th-century castelo has sweeping views over the village rooftops and river. Inside the grounds is the Núcleo Museológico de Arqueologia (Archaeological Museum), displaying ruined medieval castle walls and other artefacts, and an exhibition on Islamic board games.
The entrance fee to the castle also includes entry to the tiny themed museums (núcleos museológicos) in Alcoutim and around.
A fort has existed here since Neolithic times, but it was established as a major fortress by the Romans in 100 AD. During the Reconquista period after 1240, the current castle began to take form. Restorations and additions continued until 1521, when it was largely abandoned once the river began silting up.